The principle of negative pressure wound therapy devices (NPWT) is to promote wound healing by applying a negative pressure on a wound area. The clinical practice of the United States in the last decade shows that the device is very effective in healing acute and chronic wounds.
Generally, a negative pressure wound therapy system includes a negative pressure wound therapy device, a wound kit and a container for collecting wound exudates (refers to a fluid collection canister). The wound kit is adapted to enclose a wound and create a negative pressure space. The negative pressure wound therapy device, including a negative pressure source and a controller, is adapted to create a desirable negative pressure space for the wound. FIG. 1 shows a common negative pressure wound therapy device, where a negative pressure wound therapy device 8 is schematically shown within the dashed box; the skin tissue around the wound is indicated by the reference number 1; the wound area is covered by a wound filler 2; a wound enclosure 3 is arranged above the wound filler 2 to enclose the wound, where the wound filler 2 is in communication with a fluid collection canister 5 via a catheter 4, hence the exudates from the wound may be guided into the fluid collection canister 5 which is adapted to collect the exudates from the wound. The other end of the fluid collection canister 5 is connected to a negative pressure source 6 which may provide a negative pressure for powering the flowing of the wound exudates into the fluid collection canister 5; the negative pressure source 6 is connected to a controller 7 which may control the negative pressure source 6. Generally, the device is characterized in that the fluid collection canister is designed to be matched with the device, i.e., the fluid collection canister is designed in various shapes, such as rectangle, to fit with the device closely. In the practical use of negative pressure wound therapy system, the exudates are required not to flow back into the negative pressure wound therapy device in a case that the fluid collection canister is full of the wound exudates, and the fluid collection canister is required to be replaced timely. Generally, the medical staff or patient needs to observe directly whether the fluid collection canister is full of fluid, which is inconvenient.